In recent years, apparatuses based on methods, such as the Moving Picture Experts Group (MPEG) for using image data as digital and compressing by discrete cosine transformation and other orthogonal transformations and motion compensation by using redundancy peculiar to image information for the purpose of efficiently transferring and accumulating information, have been widespread both in information distribution by broadcast stations and in information receiving by general households. In the MPEG method, transformation coefficients are generated by performing orthogonal transformation on image data to be coded and quantization is performed on the transformation coefficients by a predetermined quantization scale, and then the quantized image data are coded.
In the MPEG method, the quantization scale is determined based on a degree of complexity of an image to be coded, so that the more complex the image becomes, the smaller the value becomes.
Following to the MPEG method, coding methods called the H.264 and JVT (Joined Video Team) for realizing a still higher compression rate have been proposed.
In the JVT method coding apparatus, coding in the JVT method is performed after decoding image data coded by the MPEG in some cases.